The long-term goal of this competing renewal application is to elucidate the molecular basis underlying cell- extracellular matrix (ECM) adhesion and regulation, and the mechanism whereby they control cell behavior, tissue integrity, growth and regeneration. Recent studies by the applicant and others have demonstrated a critical role of kindlin-2 (also known as Mig-2), a widely expressed membrane-cytoskeleton junctional protein, in integrin activation and cell-ECM adhesion. How kindlin-2 regulates these processes, however, is not known. Based on findings obtained during previous project periods, the applicant hypothesizes that kindlin-2 regulates these processes through interacting with membrane lipids and protein components of cell-ECM adhesions. To test this hypothesis, he proposes studies with the following three aims. Aim 1 is to characterize the interaction of kindlin-2 with membrane lipids and assess its role in regulation of integrins and integrin-dependent processes. To this end, he will employ genetic, pharmacological and dominant negative inhibition strategies to ablate this interaction, and determine the consequences. Aim 2 is to determine the functions of kindlin-2 interactions with focal adhesion proteins in regulation of cell-ECM adhesion. He will define the sites mediating the interactions and use a knock-in strategy to replace wild type kindlin-2 with mutants lacking specific protein-binding activity and determine the consequences. Aim 3 is to investigate the functions of kindlin-2 and its interplay with ILK in liver structure, growth and regeneration, which are known to be regulated by ECM adhesion and ILK signaling. He will generate hepatocyte-specific kindlin-2 knockout and knock-in mice, in which wild type kindlin-2 is substituted with kindlin-2 mutants lacking specific binding activities, and determine contributions of kindlin-2 and its interactions to regulation of hepatocyte behavior, liver structure, growth and regeneration. These studies will fill important gaps in our understanding of the mechanism whereby cell-ECM adhesion and ECM-dependent tissue processes are regulated. Given the importance of cell-ECM adhesion in human diseases, these studies may also lead to novel approaches to control diseases associated with abnormal cell-ECM adhesion and signaling.